Preoperative risk factors associated with symptomatic pulmonary embolism after total knee arthroplasty.

This retrospective case-control study reviewed 124 consecutive patients undergoing cemented total knee arthroplasty under regional anesthesia for osteoarthritis. Seven (5.6%) patients developed symptomatic pulmonary embolism despite warfarin prophylaxis. Bilateral procedures and preoperative hemoglobin were identified as significant risk factors for the development of symptomatic pulmonary embolism after total knee arthroplasty (hemoglobin > or =14 g/L, odds ratio 2.4, confidence interval [CI] 1.2-4.6, and bilateral cases odds ratio 7.2, CI 1.3-39.6). Additionally, preoperative hemoglobin <14 gm/L was associated with a 98% negative predictive value of developing symptomatic pulmonary embolism with a 14% false-negative rate (sensitivity 85.7%, 95% CI 80-92; specificity 67.9%, 95% CI 60-77; positive predictive value 14%, 95% CI .08-2). These findings indicate preoperative hemoglobin levels should be considered in addition to the usual patient demographics in future thromboembolism studies as a potential risk factor for symptomatic pulmonary embolism.